fix gzip-plain-gzip case

in vped_deliver, we used the wrong gzip state pointer for ESI objects,
which lead to the pretendgzip filter not being pushed.

Also, we should respect the RES_ESI bit to properly handle the case when
esi is deactivated on an esi object. (to be tested)

src/vdp_pesi.c

@@ -1267,10 +1267,7 @@ vped_deliver(struct req *req, struct boc *boc, int wantbody)
 	obj_esi = ObjHasAttr(req->wrk, req->objcore, OA_ESIDATA);
 	obj_final = (req->objcore->flags & OC_F_FINAL) != 0;
 
-	if (obj_esi)
-		gz = &node->nexus.gzip;
-	else
-		gz = &parent->nexus.gzip;
+	gz = &parent->nexus.gzip;
 
 	if (gz->is && obj_gzipped && !(req->res_mode & RES_ESI)) {
 		/* OA_GZIPBITS are not valid until BOS_FINISHED */
@@ -1304,8 +1301,9 @@ vped_deliver(struct req *req, struct boc *boc, int wantbody)
 		gz = NULL;
 	}
 
-	if (obj_esi) {
+	if (obj_esi && req->res_mode & RES_ESI) {
 		VSLdbg(req, "vped_deliver: ESI");
+		AZ(vgzgz);
 
 		// VDP_pesi + buf has been pushed from VCL
 		push_vdps(req, vgzgz, gz);